The present invention relates to an integrated opto-electronic relay using a semiconductor with persistent photoconductivity and a matrix of such relays. It is used in the switching of electrical signals.
Switching is generally carried out by electromechanical or electromagnetic relays. However, these devices are not entirely satisfactory, because they have large dimensions and require a by no means negligible power supply.
The present invention relates to a switching element obviating these disadvantages. For this purpose, the invention uses semiconductors which permit extensive integration and require only low control and holding energy levels.
The essential element of the relay according to the invention is a layer of material having the persistent photoconductivity phenomenon. This phenomenon is theoretically described in the following articles:
R. J. NELSON, Appl. Phys. Lett. 31, 5, 315, 1977; PA1 D. V. LANG, R. A. LOGAN, Phys. Rev.Lett. 39, 10 635, 1977 PA1 U. PIEKARA, J. M. LANGER Sol. Stat. Comm. 23, 583, 1977 PA1 R. LEGROS, Y. MARFAING, R. TRIBOULET J.Phys.Chem.Solids 39, 179, 1978. PA1 B. BALLAND, G. VINCENT, D. BOIS, Appl. Phys. Lett. 34. 108. 1979.
The use of the material having persistent photoconductivity for producing an opto-electronic device is not novel per se. French Patent application No. 2,396,420 filed on June 29th 1977 and entitled "Transparent photoconductor material, its production process and devices using it" describes for example a "memory device" using as the photoconductor material a substoichiometric amorphous oxide of a metal belonging to group VI and more particularly a tungsten oxide.
Such a device has numerous disadvantages through the use of this type of oxide as the photoconductor material. Firstly, it is not suitable for the integration of its elements and it therefore has large dimensions. Furthermore, the excitation radiation is necessarily in the ultraviolet, which makes the excitation source difficult to use. Finally, the heating of the photoconductive layer, as a result of which it is possible to eliminate the conductivity of the material, can only be obtained by a means separate from that of the ultraviolet source.